This invention relates to an automated process and facility for treating or sterilizing foods, nutrients, potables, medicine and other products by gamma-irradiation. It provides automatic controls for monitoring, transporting, and irradiating such materials in predetermined programs designed for adequate and uniformly effective processing or sterilization.
Gamma radiation for commercial or industrial treatment or sterilization of food substances has been increasingly utilized since its inception in several countries since the 1970's. The commercial application of irradiation to sterilize medical devices has been applied on a worldwide basis because of a continuing concern about the side effects and safety of some of the chemical fumigants vis-a-vis contact with the population in general and also accumulation in the food chain. Irradiation of pork, poultry, grain, potatoes, fruits and vegetables, enzymes, herbs, and spices has been approved by the U.S. Food And Drug Administration. The approval of this treatment has recently been broadened to encompass the disinfestation and shelf-life extension of fruits and vegetables and to increase the maximum doses for spices.
Gamma radiation was first observed at the turn of the century and shows many similarities to x-rays. It is, however, of a shorter average wavelength and due to spontaneous disintegration of radioisotopes. Most commonly, Cobalt-60 and Cesium-137 are used as radiation sources for a variety of medical and industrial applications, including sterilization.
Small doses of gamma radiation are found sufficient to eliminate the viability of virtually all types of microorganisms, its efficiency being comparable to extreme heat or chemical sterilants. "Rad" is the basic measure for "the radiation absorbed dose" as the amount of irradiation received by a product under treatment. Typically, doses administered may range from a low of 6 kilorads (6000 rads) for sprout inhibition or 25 kilorads (25,000 rads) for insect disinfection of fruit to 2.5 megarads (2,500,000 rad) used for the sterilization of medical products.
The advantages of gamma irradiation as a method of processing or sterilization reside in the limited number of variables that have to be controlled as it is independent of temperature, pressure and humidity. Gamma rays can penetrate all forms of packaging materials, including glass and metal containers. Thus foods and the like can be treated uniformly and quickly. At the dosage required for food processing and medical-product sterilization, the molecular structure of these products, is not adversely affected. Moreover, the internationally approved or U.S. approved gamma irradiation process cannot cause any material being irradiated to become radioactive.
In order to preserve the nutritious quality of foodstuffs or efficacy of medical and pharmaceutical products during irradiation, the process should involve a great deal of flexibility and adjustability depending on the required radiation dosage.
The U.S. Pat. No. 4,029,967 describes a device wherein a radiation source, such as cobalt-60, is surrounded in a circle by an array of shielding means and gaps for controllably irradiating the various goods which are positioned in adjacent cylindrical or box containers. As the distance between radiation source and radiation target center remains constant, the containers must be intermittently or continuously rotated as well as relocated in the circle around the radiation source and shielding means to avoid overdosing the goods.
Another approach has been to irradiate the materials by moving them in pallets sequentially on two parallel tracking paths past the radiation source in the source rack, such that first one side and then the other will be exposed for an appropriate amount of time. Given the various dose requirements for different materials being irradiated, location of the pallets close to the gamma radiation source can result in damage to more exposed sections when trying to achieve desired minimum doses.
Moreover, large changes in the required product dosage in the known systems would entail hazardous manipulation or exchange of the intensity or strength of the radiation material. This complicated manipulation of the sterilization process thereby resulted often in loss of time, value, and overall efficiency.
Moreover, with the growing need for efficiently keeping track of the product location and treatment within the official regulations, the ability to measure and monitor the irradiation process has paramount importance and thus spawned the development of computerized technologies.
The problem of the desirable uniformity of irradiation and concomitant efficacy in treatment has led to intensive search for an automated dosimetry of irradiation combined with mechanical features which allow ease of handling and greater economy as well as safety in the use of the irradiator.